Apex domains cannot have CNAME records.
Question and response
Question
dig china-sea.org. NS
Answer
china-sea.org. 5 NS ns-6.awsdns-00.com.
china-sea.org. 5 NS ns-531.awsdns-02.net.
china-sea.org. 5 NS ns-601.awsdns-11.net.
china-sea.org. 5 NS ns-1442.awsdns-52.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0